1. Field of the Invention
This invention relates to a high-speed gun drill.
2. Description of the Related Art
Gun drills for drilling deep holes usually have a reversed taper of approximately 0.01 mm per 100 mm from the tip to the base end thereof. The reversed taper is provided to assure smooth drilling by preventing frictional contact between the peripheral surface of the gun drill and the inner surface of the hole being drilled.
When deep holes are drilled by rotating gun drills of this type at high speeds, however, large torques acting on cutting edges of the drills often cause axial runout or flexing. Then, it becomes practically impossible to continue high-speed drilling at a speed of, for example, 1100 mm per minute.